Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objExcel = CreateObject("Excel.Application")
objExcel.DisplayAlerts = False

strFolder = "E:\user\WeChat Files\WeChat Files\wxid_vu6eu977ndi121\FileStorage\File\2021-04\"
strFolder2 = "E:\user\WeChat Files\WeChat Files\wxid_vu6eu977ndi121\FileStorage\File\2021-04\csv\" 

Set objFiles = objFSO.GetFolder(strFolder).Files
For Each objFile In objFiles
    If Lcase(Split(objFile.Name, ".")(1)) = "xls" Then
        Set objWorkbook = objExcel.Workbooks.Open(strFolder & objFile.Name)
        For Each sheet In objWorkBook.Sheets
           If objExcel.Application.WorksheetFunction.CountA(sheet.Cells) <> 0 Then
              objWorkbook.SaveAs strFolder2 & Split(objFile.Name, ".")(0) & "_" & sheet.Name & ".csv", 6
            End If
        Next
        objWorkbook.Close
    End If

Next

objExcel.Quit


